C# Desktop graphics

I want to highlight the mouse cursor with a red dot, but the program only draws on 3/4 of the screen. If I move the cursor to the right side of the screen, the red dot disappears. Can anyone help me, how to "use" the whole screen?

[DllImport("User32.dll")]
public static extern IntPtr GetDC(IntPtr hwnd);

public void moveCursor()
    {

        while (true)
        {
            System.Windows.Point pMouse = MouseControl.GetCursorPosition();
            if (pMouse != null)
            {

                IntPtr desktopPtr = GetDC(IntPtr.Zero);
                this.x = (int)pMouse.X;
                this.y = (int)pMouse.Y;
                using (Graphics g = Graphics.FromHdcInternal(desktopPtr))
                {
                    g.FillEllipse(action ? Brushes.Blue : Brushes.Red, (int)(x * 1.25 - 27 / 2), (int)(y * 1.25 - 27 / 2), (int)(27 * screen), (int)(27 * screen));

                }
                ReleaseDC(IntPtr.Zero, desktopPtr);
            }

            Thread.Sleep(5);
            ToggleDesktopIcons();
        }
    }